Causes of Climate Change
Earth's atmosphere contains various gases that act as a blanket to trap heat from the sun and prevent it from escaping back into space. This process is known as the greenhouse effect, and the gases are referred to as greenhouse gases. The main greenhouse gases that occur in nature are carbon dioxide, methane, and nitrous oxide. Without the greenhouse effect, the planet would be too cold to support life. Over time, the amount of greenhouse gases trapped in Earth's atmosphere has increased significantly, causing worldwide temperatures to rise.
Natural processes on Earth constantly create and destroy greenhouse gases. The decay of plant and animal matter, for example, produces carbon dioxide, which plants then absorb during photosynthesis. This natural cycle keeps the level of carbon dioxide in the atmosphere fairly stable. Shifts in the planet's crust and changes in ocean patterns impact weather, as do fluctuations in the sun's output of radiation. Volcanic activity also affects the climate because eruptions discharge greenhouse gases and other pollutants into the atmosphere. Climate change scientists at the National Aeronautics and Space Administration (NASA) and other federal and international agencies recognize that these natural factors continue to play a role in climate change but contend that the impact of these factors alone does not explain the substantial rise in Earth's temperature. Natural causes of climate change are referred to as naturogenic, while human-made causes of climate change are referred to as anthropogenic.
Earth's vegetation releases and absorbs more than two hundred billion metric tons of carbon dioxide annually. Human activities, such as the burning of fossil fuels, add an extra seven billion metric tons per year. Over time, these additions have had a dramatic effect on the atmosphere. In the past 150 years, the concentration of carbon dioxide in the atmosphere has risen by more than 30 percent. Deforestation has also played a role in this increase by eliminating forests that would otherwise absorb tons of carbon dioxide.
Increased levels of other greenhouse gases such as nitrous oxide and methane have also resulted from human activities. Several agricultural and industrial activities, such as the use of certain fertilizers in agriculture, produce nitrous oxide. Methane emissions come from the production of fossil fuels, from landfills, and from livestock. These gases may cause even more harm than carbon dioxide, even though less of them exist, because they have a much greater effect per pound on Earth's temperature. Methane, for example, is a greenhouse gas that is twenty-one times as potent as carbon dioxide. Beginning in October 2015, a methane gas leak from a California storage facility vented about five billion cubic feet of gas into the atmosphere. The leak took more than three months to seal and was finally capped on February 18, 2016. The incident constituted the largest accidental discharge of greenhouse gases in US history, releasing the equivalent of the yearly exhaust emissions from 572,000 automobiles.
Humans have created and released greenhouse gases that do not occur in nature. These include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). These gases, released during such industrial processes as aluminum production and electrical transmission, have thousands of times greater effect on the planet's temperature than carbon dioxide.
Climate Change Predictions
Climate science measures changes that occur to a large geographical area over a long period of time, making it difficult to provide definitive answers to climate change questions. However, multiple studies have been conducted since the 1990s to determine how the scientific community collectively views anthropogenic climate change. These studies included surveys as well as analyses of peer-reviewed articles and have concluded that at least 97 percent of actively publishing climate scientists around the world agree that human activities have contributed to rising global temperatures.
Though surveys indicate that many Americans remain skeptical toward arguments and evidence put forth by climate scientists, reports suggest that belief in global warming has grown steadily in the twenty-first century. According to annual polls conducted by Gallup, the public's belief that global warming is caused by human activity, that climate change has begun to take effect, and that global warming will soon pose a serious threat has increased since 2001. Researchers have observed a strong correlation between people's political affiliations and their levels of concern regarding global warming and acceptance of climate science. A total of 64 percent of all Americans polled reported a belief that human activity contributes to global warming in 2018, which included 89 percent of Democrats, 62 percent of independents, and 35 percent of Republicans. Similarly, 91 percent of Democrats responded that they worried significantly about global warming, compared to 62 percent of independents and 33 percent of Republicans. Democrats also reported much higher confidence (86 percent) that scientists have reached a consensus that global warming is real than Republicans (42 percent). Gallup's polling further indicates that people age 55 and older are more likely than younger respondents to believe that the media exaggerates the threat of climate change.
Skeptics of global warming and climate change have noted that Earth has experienced cyclical changes to its climate patterns for millennia and that recent climatic shifts are not as severe as indicated or necessarily a consequence of human activity alone. Climate scientists contend that such skepticism may stem from an unwillingness to face the scope of the threat posed to the planet by human activity. Additionally, conservative donors, including several foundations established by wealthy families, have contributed large amounts of money to organizations that promote climate change denial. Foundations linked to the prominent Koch family, for example, donated over $100 million to such organizations between 1997 and 2015, as reported by the environmental organization Greenpeace.
Even if all members of society agreed that global temperatures are rising and humans are the cause, the challenges created by climate change lack an obvious solution. No climate model formulated by scientists to chart climate patterns has had 100 percent accuracy in predicting changes. However, scientists continue to refine their methods to produce more reliable data. Most climate models failed to predict a slowdown in rising temperatures at the beginning of the twenty-first century. Some predictions have also underestimated threats. In its initial assessment of rising sea levels in 1990, the Intergovernmental Panel on Climate Change (IPCC) originally anticipated a sea-level rise of 1.9 millimeters per year from that year onward. However, studies by NASA have revealed that sea levels have in fact risen at a rate of 3.2 millimeters per year. The science of climate change is so complex that some actions that seem helpful may cause damage in the long term. Some of the most potent greenhouse gases, HFCs and PFCs, are commonly used as replacements for other chemicals called chlorofluorocarbons (CFCs), which were phased out between 1989 and 1996 because they damaged the ozone layer. Consequently, the same process that solved one environmental problem—ozone damage—contributed to another.
Effects of Global Warming
The consequences of global warming remain an issue of great debate and uncertainty, and some researchers predict dramatic and serious problems for future generations. Warmer oceans could result in stronger and more frequent hurricanes. As temperatures climb, some regions could experience frequent heat waves and devastating droughts and wildfires. During the 1990s and first decade of the twenty-first century, many areas in the United States endured record-breaking heat and drought. In 2012, severe drought plagued the Wheat Belt of the United States, located in the North American Great Plains. In the beginning of 2013, Australia experienced a heat wave that caused hundreds of wildfires throughout the country. Climate change has also been linked to the severe drought that occurred in California between 2011 and early 2017. In 2018 California has further endured massive wildfires that have led to the displacement of thousands of residents, widespread destruction of property, and the deaths of at least eight people. Scientists have attributed the fires, which included the largest wildfire in California history to date, to the presence of extremely dry vegetation, brought on by rising temperatures, that created conditions that allowed the fires to spread rapidly and burn intensely. California governor Jerry Brown lamented that such fires have become increasingly common in the southwestern United States and warned that fires would likely become more intense as climate change continues.
Many coastal areas around the world could also face severe flooding due to rising sea levels. Low-lying islands in the Pacific Ocean would eventually become uninhabitable. Within the past century, sea level has risen by four to eight inches worldwide. Some of these effects were felt in 2012 when a super storm known as Superstorm Sandy hit the Eastern coast of the United States, and a typhoon in the Philippines claimed the lives of more than one thousand people. The hurricane season of 2017 proved to be the costliest hurricane season since 1900, with severe weather and rising sea levels leading to tragic loss of life and over $215 billion of property damage in Florida, Texas, and Puerto Rico as well as other states in the Southeast and several countries located in Central America and the Caribbean.
Global warming could also have a major impact on habitats. Some areas well suited to farming might become too dry or too wet to support agriculture. Long periods of drought could turn fertile lands into deserts with little vegetation. Plants and animals might not be able to survive the rapid changes caused by global warming and could become extinct. Over the long term, such changes would result in a loss of biodiversity on the planet. Some ecosystems, such as coral reefs and coastal mangrove swamps, are likely to disappear completely.
Furthermore, people would also face serious problems. Loss of farmland, for example, would cause disruptions in the food supply, bringing about famine in many areas. Scientists have noted that various species of disease-carrying mosquitoes have expanded their habitats to areas where they could not have lived before the rise in atmospheric temperature. More frequent and intense heat waves could result in more heat-related deaths, and changes in air quality could also affect human health. A 2018 study in the environmental science journal Nature Climate Change determined that rising temperatures are contributing to increased rates of suicide, anticipating that the trend will continue without a widespread response to climate change that addresses the impact of humans on the environment.
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